Pulpwood chipper

ABSTRACT

Wood chipper has rotating chipper disc and fan wheel spaced from disc against which fan wheel chips impinge. Fan wheel provided with impact plates in area of impact of chips to provide low angle of impact to impinging chips to minimize chip damage.

[ 1 Aug. 8,1972

United States Patent Smith References Cited UNITED STATES PATENTS [s41 PULPWOOD CHIPPER [72] Inventor: William C. Smith, West Vancouver,

British Columbia, Canada 731 Assignee: Rader Pneumatics & Engineering 3,384,311 5/1968 Eklund et a1. ......241/56 co. Ltd Burnaby, British Comm 3,410,495 7 11/1968 Eklund........ ............241/56X bia,Canada Primary Examiner-Granville Y. Custer, Jr.

[22] Wed: Feb. 3, 1971 [21] Appl.No.: 112,310

ABSTRACT [52] U.S. Cl;.......... ....24l/56, 241/278 R o chipper has rotating chipper disc and fan wheel [51] Int. 18/06 spaced from i against whi h f wheel hip imp- [58] Field of Search.....241/56, 277, 278 R, 280, 281 inge. Fan wheel provided with impact plates in area of impact of chips to provide low ang1e of impact to impinging chips to minimize chip damage.

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IO 32 1' I (I l I 22 WILLIAM C. SMITH JSNVENIOR BUCKHORN, BLORE, KLARQUIST & SPARKMAN ATTORNEYS P'A'IENTEDAUB 8 Ia 3,682,400

sum 2 or 2 BUCKHORN, BLORE, KLARQUIST & SPARKMAN ATTORNEYS NVENTOR WILLIAM; C. SMITH v PULPWOOD CHIPPER BACKGROUND OF THE INVENTION In the making of paper pulp from wood and particularly in utilizing a chemical pulping process it is desirable that the wood chips be uniform in size both in width and length as well as in thickness, and that the chips have a minimum content of small slivers or pins and sawdust-like particles.

Wood chips are conventionally obtained by passing logs or wood scraps through a chipper which comprises a massive rotating disc having radially extending knives arranged to cut off the ends of the wood or logs fed into the chipper. The disc is provided with passageways adjacent the knives so that the severed chips may pass to the rear of the disc. In one type of chipper a fan wheel is mounted behind the disc and is provided with blades which are adapted to engage and propel the chips and also the surrounding air so as to blow the chips out of DETAILED DESCRIPTION OF THE INVENTION The illustrated chipper comprises a chipper disc mounted on a horizontal shaft 12 which may be driven by any suitable drive means (not shown). The shaft 12 is suitably supported as by trunnions 14 which in turn are suitably supported on a rigid base (not shown). The

' illustrated chipper is of the horizontal infeed type havthe chipper and for a substantial distance therefrom.

The geometry of prior chippershas been such that the blades have engaged the chips with a relatively high differential velocity with substantial damage to the chips and production of large amounts of undesirable slivers, pins and sawdust-like particles. In addition, in prior chippers the chips have impacted against the side surface of the fan wheel at a relatively high velocity and a high incidence angle causing further breakage of the chips.

BRIEF DESCRIPTION OF THE INVENTION travel towards the fan wheel in short bursts along thesame path and will strike the fan wheel adjacent its The chipper disc 10 may be of any conventional construction and is provided with a plurality of removably mounted knives 28 which project from the front face thereof, the disc having openings or slots 29 (FIG. 4) adjacent to each of the knives through which the severed chips may pass from the front to the back of the disc 10 as they are severed from logs fed through the infeed spout 20.

Mounted on the shaft 12 rearwardly of the disc 10 with respect to the spout 20 is a wheel 30 which may be, for example, a flywheel or fan wheel. The fan wheel periphery in areas spaced around the wheel as such DRAWINGS FIG. 1 is a perspective, semi-schematic view of a chipper constructed in accordance with the invention with certain parts indicated in phantom and others.

broken away to illustrate certain details;

FIG. 2 is a horizontal section on a reduced scale of a chipper constructed in accordance with the invention,

FIG. 3 is an enlarged fragmentary perspective view of the fan wheel; and,

per second, or about 4,900 centimeters per second.

30 is enclosed within a housing 32 provided with a tangential outlet 34 at the top thereof. The fan wheel 30 is provided with a plurality of impeller or fan blades 36 having a portion extending outwardly from the periphery of the wheel but also having a portion which extends outwardly from the side face 38 of the wheel 30 adjacent the chipper disc 10. The peripheral portion at least of the face 38 is planar and perpendicular to the axis of rotation of the wheel 30. The housing 32 is coaxial with the fan wheel 30 and the blades 36 are'sized so as to provide relatively close clearance between the housing and the edges of the blades to prevent accumulation of chips between them. Extending between and communicating with the disc housing 22 and the fan wheel housing 32 is a tunnel 40 through which chips may pass as they are severed by the cutter disc 10.

In a chipper of the type illustrated, the cutter disc 10 is rotated at a relatively high velocity, for example, at a speed of from 200 to 720 revolutions per minute and the disc may have a diameter up to 3,000 centimeters. A chip which is severed from a log or other piece of wood has a velocity imparted to it which is roughly 20 percent greater than the tangential velocity of the knife 28 at the point of impact. Thus, in a chipper rotating at 300 rpm and having a cutter disc diameter of 3,000

centimeters, a chip cut from a piece of wood contacted by a knife at a point near the periphery of the cutter disc can have a velocity in the order of about 156 feet Chips cut in positions closer to center of the disc 10 will have a lesser velocity. Chips of the higher velocities which are severed with a chipper such as illustrated will sufl'er substantial damage when they impact upon a sur- FIG. 4 is an enlarged fragmentary view of the chipper pulp making process.

disc and fan wheel illustrating the chip path.

face at a large angle, that is, an angle greater than about 45. By-damage is meant fracture and rupture of the chips so as to form small fines and particles which are unsuitable in the making of pulp andinterfere with the Chips severed from the raw material pass through the slots 29 in the disc adjacent each of the knives in a substantially uniform path. In the chipper of the invention the disc 30 is positioned so that the path of the chips will be intercepted by the disc adjacent the periphery thereof. As will be apparent, the chips will travel in bunches, that is, each knife will cut off a group of chips which will pass through the opening adjacent the knife. There will be a short interval of time between each group of chips as one knife leaves the cutting position and the next knife on the disc reaches the cutting position.

Accordingly, the chips will impact upon the disc 30 at circumferentially spaced areas adjacent its periphery there being an impact area for each of the knives. Such impact areas are quickly discernible when a cutter is put into operation by the evidence of wear or removal of paint upon the surface of the wheel 30 at the areas of impact.

With most chips severed in a chipper of the type described and particularly with the chips to which higher velocities are imparted, the angle of impact on the surface 38 of the disc 30 is so great as to cause damage. This angle may be of the order of 60. F urthermore, while the chips have a tangential component of motion in the direction of rotation of the fan wheel 30, this velocity component is substantially less than the velocity of the fan wheel 30 as a consequence of which radial blades striking such chips may have a substantially high relative velocity and cause damage to such chips.

Accordingly, in accordance with the present invention such chip damage is minimized by providing impact means on the surface of the fan wheel 30 facing the cutter disc which define impact surfaces for the chips having an included angle with respect to the path of travel of the chips less than about 40 whereby the chips suffer minimum damage upon impact. Referring to FIGS. 3 and 4, in accordance with the invention, the fan blades 36 are positioned around the periphery of the wheel 30 so that there is one fan blade 36 adjacent to but rearwardly of each impact area on the peripheral portion 38. The blades 36 each comprise an L-shaped plate 44 including a fan portion 46 which extends radially upwardly from the periphery of the wheel 30 and also extends beyonds the face 38 of the wheel 30 toward the cutter disc 10. The plate 44 also includes a leg 47 which extends radially inwardly along the wheel face 38. The plate 44 is secured to the flywheel 30 by a flange 48 extending from the leg 47 alongithe face 38 and bolts 50 extending through the flange 48 and wheel 30. The plate 46 is braced by gussets 52 and a backup plate 54 extending across the periphery of the wheel 30. Extending angularly inwardly from the top edge of the leg 47 of each of the plates 36 toward the side surface of the wheel 30 is a plate 60. The plate 60 is angled such that its angle of impact with a chip having a path shown in dotted line 62 (FIG. 4) coming from a knife 28 will be less than 40 and preferably at an angle less than about 35. The plate 60 is planar in its upper portion and has a flat toe 64 extending along the surface 38 of the wheel 30. The toe 64 is secured by bolts to the wheel 30 the head portion of which bolts is preferably recessed in the surface of the plate so asto provide no projecting impacting surface. The forward edge of the flat toe 64 is tapered as indicated at 68 for the same reason and preferably a curved transition section 66 is provided between the toe 64 and the main portion of the plate 60. Chips striking the plate along the trajectory 62 will rebound at an angle approximately half of the impact angle and thus will be projected forwardly in a direction substantially parallel to the side surface 38 of the wheel 30 and in its direction of rotation. Some will tend to slide along the plate and the transition 66 is provided to assist in the smooth transfer of the chips to the surface 38. The direction of impact will also be towards the periphery of the wheel so that the chips will eventually be engaged by the fan portion 46 of the wheel and be blown out of the top exit 34.

Provision of low impact surfaces as defined by the plate 60 will result in substantial reduction in the percentage of fines which are produced in the chipping operation.

Having illustrated and described a certain preferred embodiment of the invention, it should be apparent that the invention permits of modification in arrangement and detail.

I claim:

1. Apparatus for producing wood chips comprising:

a rotary cutter disc having a plurality of substantially radial knives along one face of said disc for cutting chips from lengths of wood fed toward said face, and passageways through said disc for permitting the severed chips to pass through said disc,

a wheel mounted on the side of said disc opposite said one face in spaced relation to and coaxially with said cutter disc, and adapted to be driven in the same direction of rotation as said disc,

said wheel being mounted so as to intercept the path of travel of chips cut by said cutter disc knives,

and impact means on the surface of said wheel facing said disc defining impact surfaces for said chips having an included angle with respect to said path of travel of less than 40.

2. An apparatus claimed in claim 1 wherein said impact means comprises plates mounted on said wheel adjacent the periphery thereof and extending at an acute angle from said wheel surface.

3. An apparatus as claimed in claim 2 wherein said plates each comprises a curved portion and a flat portion extending at an acute angle from said wheel surface, said curved portion providing a transition between said wheel surface and said flat portion.

4. An apparatus as claimed in claim 1 wherein said wheel has a plurality of fan blades extending therefrom for accelerating chips and air so as to convey the chips a substantial distance from the apparatus.

5. An apparatus as claimed in claim 3 wherein said flat portion extends at an angle of about 30 with respect to a plane normal to the axis of rotation of said wheel.

6. Apparatus for producing wood chips comprising:

a rotary cutter disc having a plurality of substantially radial knives along one face of said disc for cutting chips from lengths of wood fed toward said face, and passageways through said disc for permitting the severed chips to pass through said disc,

a wheel mounted on the side of said disc opposite said one face in spaced relation to and coaxially with said cutter disc, and adapted to be driven in the same direction of rotation as said disc,

said wheel being mounted so as to intercept the path an impact surface defining plate sloping from the oftrayelofchips f y Said cutter disc i outer edge of each of said fan blades to said s p gm of 3 5 33 sad X11661 peripheral surface portion in the direction of rotaacmg sai sc emg su l y p anar an perpendicular to the axis ofrotafion, 5 tion of sa1d wheel whereby chips severed at said disc will impact on said plate and be accelerated a plurality of fan blades mounted on said wheel and projecting from Said peripheral surface ponion of thereby in the direction of rotation of said wheel. said wheel toward said disc, 

1. Apparatus for producing wood chips comprising: a rotary cutter disc having a plurality of substantially radial knives along one face of said disc for cutting chips from lengths of wood fed toward said face, and passageways through said disc for permitting the severed Chips to pass through said disc, a wheel mounted on the side of said disc opposite said one face in spaced relation to and coaxially with said cutter disc, and adapted to be driven in the same direction of rotation as said disc, said wheel being mounted so as to intercept the path of travel of chips cut by said cutter disc knives, and impact means on the surface of said wheel facing said disc defining impact surfaces for said chips having an included angle with respect to said path of travel of less than 40*.
 2. An apparatus claimed in claim 1 wherein said impact means comprises plates mounted on said wheel adjacent the periphery thereof and extending at an acute angle from said wheel surface.
 3. An apparatus as claimed in claim 2 wherein said plates each comprises a curved portion and a flat portion extending at an acute angle from said wheel surface, said curved portion providing a transition between said wheel surface and said flat portion.
 4. An apparatus as claimed in claim 1 wherein said wheel has a plurality of fan blades extending therefrom for accelerating chips and air so as to convey the chips a substantial distance from the apparatus.
 5. An apparatus as claimed in claim 3 wherein said flat portion extends at an angle of about 30* with respect to a plane normal to the axis of rotation of said wheel.
 6. Apparatus for producing wood chips comprising: a rotary cutter disc having a plurality of substantially radial knives along one face of said disc for cutting chips from lengths of wood fed toward said face, and passageways through said disc for permitting the severed chips to pass through said disc, a wheel mounted on the side of said disc opposite said one face in spaced relation to and coaxially with said cutter disc, and adapted to be driven in the same direction of rotation as said disc, said wheel being mounted so as to intercept the path of travel of chips cut by said cutter disc knives, the peripheral portion of the surface of said wheel facing said disc being substantially planar and perpendicular to the axis of rotation, a plurality of fan blades mounted on said wheel and projecting from said peripheral surface portion of said wheel toward said disc, an impact surface defining plate sloping from the outer edge of each of said fan blades to said peripheral surface portion in the direction of rotation of said wheel whereby chips severed at said disc will impact on said plate and be accelerated thereby in the direction of rotation of said wheel. 